void TestR6()
        {
            "Demonstrating Requirement #6".title();
            Write("\n --- Test sheduler---");
            dbInt.showDB();
            PersistWapper <int, DBElement <int, string> > persist = new IntAndString(dbInt);
            Schedular <int, DBElement <int, string> >     test    = new Schedular <int, DBElement <int, string> >();

            Write("\n persist database in ./DatabaseContent2.xml");
            test.autoSave(persist, 1000, "DatabaseContent2.xml");
            ReadKey();
            WriteLine();
        }
        static void Main(string[] args)
        {
            DBElement <int, string> elem1 = new DBElement <int, string>();

            elem1.descr     = "payload desxription";
            elem1.name      = "element 1";
            elem1.timeStamp = DateTime.Now;
            elem1.payload   = "a payload";
            DBElement <int, string> elem2 = new DBElement <int, string>("Darth Vader", "Evil Overlord");

            elem2.descr     = "star war 2";
            elem2.name      = "element 2";
            elem2.timeStamp = new DateTime(2015, 9, 10, 12, 30, 1);
            elem2.payload   = "The Empire strikes back!";
            var elem3 = new DBElement <int, string>("Luke Skywalker", "Young HotShot");

            elem3.name      = "element 3";
            elem3.descr     = "star war 3";
            elem3.timeStamp = new DateTime(2015, 10, 2, 8, 0, 0);
            elem3.children  = new List <int> {
                1, 2, 3
            };
            elem3.payload = "X-Wing fighter in swamp - Oh oh!";


            int        key    = 0;
            Func <int> keyGen = () => { ++key; return(key); };  // anonymous function to generate keys

            DBEngine <int, DBElement <int, string> > db = new DBEngine <int, DBElement <int, string> >();
            bool p1 = db.insert(keyGen(), elem1);
            bool p2 = db.insert(keyGen(), elem2);
            bool p3 = db.insert(keyGen(), elem3);

            WriteLine("--- Test Scheduler ---");
            PersistWapper <int, DBElement <int, string> > persist = new IntAndString(db);
            Schedular <int, DBElement <int, string> >     test    = new Schedular <int, DBElement <int, string> >();

            test.autoSave(persist, 1000, "DatabaseContent.xml");
            ReadKey();
        }